Systems engineering is not a new discipline for automotive OEM’s and suppliers. However, given the increasing complexity of today’s vehicles, it is experiencing a rebirth. New approaches to mobility, sustainment and infotainment have forced the need for new and complex combinations of electrical, software and mechanical know-how. Whereas back in the 1990s, satisfying a single requirement affected a single commodity, today it can affect five or more commodities, creating threads of connectivity between systems, requirements, functions, and test procedures. Controlling this organic complexity requires an engineering discipline that can provide a collaborative business methodology that manages all the multi-disciplinary domains of engineering and development from a holistic point of view.
Systems engineering in its current approach has really been a reactive change process with ineffective traceability back to the requirements given the multiple heterogenous software tools, as well as little to no connected validation of the sub-systems. There has been no ability to test what happens to the whole when a single part malfunctions, and make adjustments within context of all the involved systems.
A Requirement, Functional, Logical, and Physical (RFLP) approach has evolved to help counteract this fragmentation and guide the vehicle architects chartered with the overall design. RFLP provides a collaborative engineering methodology that can capture, manage and track product requirements with full traceability, all from one engineering desktop window. Based upon a single, open, and scalable service oriented architecture platform, RFLP provides a unified infrastructure to share whole data across the specific discipline. With this approach, changing the product and/or requirements is completely traceable as to how it impacts the other systems.
Dassault Systèmes’ RFLP Basics
To begin the process, “R” requirements – whether corporate, end-user, financial, design manuals, guides, etc. –are defined within the authoring environment. The system architects can then pull from these requirements to define the functional and logical aspects of a product and link them to the physical definition of a product, ensuring full traceability from product specifications to the actual 3D design.
Once the requirements are defined, system architects begin the “F” functional decomposition of the product in dedicated editors. This describes “what” functions must be performed to satisfy the requirements. This is developed as a reuseable template against which the program requirements are linked. This then enables the impact of any change to be seen and aids in the decision making process.
The next step — the “L” logical piece defines “how” the functional requirement will be achieved — and there can be multiple ways to achieve the requirements. At this stage, users can use a first level of 3D representation of the system in order to perform space reservation and check specific requirements.
Within the Dassault Systèmes RFLP engineering methodology, embedded technology provides specialized modeling and simulation tools (dynamic behavior modeling based on the Modelica language and Logic & Control for reactive systems). So, as each logical entity is defined and identified, a dynamic behavior is assigned by attaching a Modelica model to each of these behaviors allowing for dynamic simulation of the behavior associated with a logical entity. Modelica allows users to conveniently model complex physical systems containing mechanical, electrical, electronic, hydraulic, thermal, electric power or process-oriented sub-components. With this capability, the model now has the physics built into it. At this logical model juncture, users can also define the control strategy. Logic & Control Modeling provides users with a formal model suited to manage parallel systems through a comprehensive set of editors. Both dynamic behaviors and Logic & Control can be co-simulated on a virtual execution platform.
Last, is the physical “P” level where actual parts are specified to execute the logical model. At this point, all engineering domains and solutions are linked together in a common and dynamic engineering template, which allows for virtual simulation and validation at any system level. Components from multiple disciplines, which may include their 3D representation as well as the numerous interactions between them, are modeled in the authoring environment to enable dynamic simulation of the complete system via a virtual prototype. So, although the functions being produced may be accomplished through different sources, everything is shown in a single model that everyone is working from.
With this approach, changing the product and/or requirements is completely traceable as to how it impacts the other systems. The requirements are directly linked to the design decision – performance, fuel economy, or cost will all directly influence the design choice. The behavior of the product in operation is assessed while various design alternatives can be tested very early on.
In our next engineering-focused blog, we’ll talk about how the RFLP approach can be applied to hybrid engine development.